Anna Brouwer

Chapter 2 38 were enrolled between August 2016 and February 2019. The authors approached 457 patients, 189 declined, 62 met the exclusion criteria and 6 withdrew. It was hypothesized that there would be an effect between short-term and long-term uveitis. To evaluate the possible effect of disease duration on the ERG, two groups were created. In group A (80 patients) an ERG was measured in the first year after disease onset, and in group B (120 patients) an ERG was measured after a disease duration of > 5 years. Disease onset was defined as the moment when an ophthalmologist first diagnosed uveitis. Patients with juvenile idiopathic arthritis (JIA) were excluded from both groups, because they were < 18 years of age at the start of disease and therefore could not be included in group A. All patients were mentally competent and gave their consent to participate. This study was conducted in compliance with the ethical principles of the declaration of Helsinki. Ethical approval was requested and obtained from the Medical Ethical Research Committee of the UMCU prior to the start of the study. ERG analysis ERGs were performed on the same day subjects visited the outpatient clinic when best corrected visual acuity (BCVA) and uveitis activity also were recorded. The ERGs were measured according to the International Society for Clinical Electrophysiology of Vision (ISCEV) standards. 5 Dawson-Trick-Litzkow (DTL) electrodes were used as corneal electrodes and placed just below the cornea, following the lower eyelid. The use of DTLs is standard procedure in the Netherlands. Compared to contact lens electrodes, the DTL provides higher patient comfort and a lesser chance of infection, while still yielding reproducible responses. 10 An Espion E3 system with colordome stimulator (Diagnosys LLC, Cambridge, UK) was used for flash stimulation. Measurements were made according to an extended ISCEV protocol, which is standard practice in the authors’ hospital. An extended protocol is useful in monitoring disease, where subtle changes must be detected. This extended protocol consists of stimuli that increase with approximately 0.5 log units steps and range from 0.0001- 30.0 cds/m 2 for dark-adapted (DA) ERGs and from 0.3-10.0 cds/m 2 for light-adapted (LA) ERGs. Also a standard a 30 Hz flicker response (LA) was recorded. The ERGs of the patients were compared to those of healthy controls (n = 158; median age 47.7 years; interquartile range (IQR) 34.3 – 57.9). These reference ERGs were provided by the Rotterdam Eye Hospital and Bartiméus (Bartiméus Diagnostic Centre for complex visual disorders, Zeist) and measured with the same protocols on an Espion E2 system. Differences between the E2 and E3 system were within the measurement error. Also, the same equipment, protocols and standard operating